He’s not kidding. Rich, a good-looking Chicago personal trainer unable to resist any sexual opportunity—his life at times resembles porn, where a car accident rapidly turns into oral sex—has wished for his genitalia to leave him alone, blaming the man downstairs for his many infidelities. (This includes his latest ex, played by Jamie Chung.) Abracadabra! Rich’s penis disappears from his body and reappears in the form of a man (Nick Thune) who behaves exactly like he did when he lived in Rich’s pants. He’s a selfish, needy, inconsiderate jerk, and Rich discovers just how accurate he was when comparing his penis to a hyper child who needs to be appeased until his parents come home ... “but his parents never come home.”

Less disgusting and a bit funnier than last year’s “Bad Milo!,” in which a man’s (Ken Marino) stress becomes a monster that crawls out of his butt, “Bad Johnson” is a nice romantic comedy disguised as a moronic raunch-fest. The chemistry between Gigandet and Katherine Cunningham, as Rich’s client and inevitable love interest, is lively in ways it often isn’t in bigger-budget love stories. (Recent example: Rashida Jones and Nick Frost in “Cuban Fury.”) There are flickers of “Hitch” and “40 Days, 40 Nights” here, peppered with vulnerability that feels sincere and a familiar-yet-worthwhile perspective on cheating.

For obvious reasons, male viewers will best identify with the plight of Rich and his pal Josh (Kevin Miller), who’s in a committed relationship and tempted by the antics of Rich’s other, dumber brain. Yet even if first-time feature writer Jeff Tetreault too often answers the question of, “How can I make this scene funnier?” with, “What if someone said something racist?” he also allows the female characters to have their own sexualities. Only Rich’s penis perpetuates outdated views of men as sex-seeking and women as sex-withholding, showing that “Bad Johnson” isn’t as stupid as the behavior it chronicles.